Controller

ABSTRACT

Booster means  11  for transmitting a force acting on a piston  10  to a valve stem  9  on amplification comprises pivotal members  25  each supported by casings  7, 8  so as to hold an outer end and an inner end thereof in contact with an outer peripheral portion of the piston  10  and a flange portion  22   a  formed on the valve stem  9  respectively from below and to be pivotally movable about a horizontal rod  26  positioned closer to the inner end. Metal bellows  16  are provided between an outer peripheral portion of the casing top wall  8   a  and the outer peripheral portion of the piston  10  for sealing off a compressed air admitting space.

TECHNICAL FIELD

The present invention relates to control devices, and more particularlyto control devices which have booster means for transmitting the forceacting on a piston to a valve stem on amplification and which aresuitable as valves for use at high temperatures.

BACKGROUND ART

Already known are control devices which comprise a valve case having afluid channel, a casing provided on an upper portion of the valve case,a valve stem disposed inside the casing and reciprocatingly movableupward and downward to thereby cause a valve element to open or closethe fluid channel, a piston upwardly or downwardly movably providedinside the casing and defining a compressed air admitting space alongwith a top wall of the casing, and booster means for transmitting theforce acting on the piston to the valve stem upon amplification (see,for example, the publication of JP-A No. 07-139648).

Control devices having such booster means are termed high-temperaturevalves and used at a temperature of at least 150° C. in some cases, butstill remain to be improved in heat resistance and have problems withrespect to sealability and durability especially for use at hightemperatures of about 300° C.

An object of the present invention is to provide a control device havingbooster means and usable at high temperatures.

DISCLOSURE OF THE INVENTION

The present invention provides a control device comprising a valve casehaving a fluid channel, a casing provided on an upper portion of thevalve case, a valve stem disposed inside the casing and reciprocatinglymovable upward and downward to cause a valve element to open or closethe fluid channel, a piston upwardly or downwardly movably providedinside the casing to define a compressed air admitting space along witha top wall of the casing, and booster means for transmitting a forceacting on the piston to the valve stem on amplification, the controldevice being characterized in that the booster means comprises at leastone pivotal member supported by the casing so as to hold an outer endand an inner end thereof in contact with an outer peripheral portion ofthe piston and a flange portion formed on the valve stem respectivelyfrom below and to be pivotally movable about a horizontal rod positionedcloser to the inner end, metal bellows being provided between the outerperipheral portion of the casing top wall and an outer peripheralportion of the piston for sealing off the compressed air admittingspace.

When the piston of the control device of the invention moves down, theouter end of the pivotal member of the booster means moves down, therebymoving the pivotal member about the horizontal rod and moving the innerend of the pivotal member upward to move the valve stem upward. With thehorizontal rod positioned closer to the pivotal member inner end, thedownward force of the piston is transmitted as amplified to the valvestem. The metal bellows used for sealing off the compressed airadmitting space obviates the need to use components, such as O-rings,which are inferior in heat resistance, while the use of the boostermeans serves to diminish the compressed air pressure acting on the metalbellows. Thus, the control device is improved in both heat resistanceand pressure resistance and made suitable as a valve for use at hightemperatures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing an embodiment of control deviceaccording to the invention.

BEST MODE OF CARRYING OUT THE INVENTION

An embodiment of the invention will be descried below with reference tothe drawing. In the following description, the terms “left” and “right”refer respectively to the left- and right-hand sides of the drawing.

FIG. 1 shows an embodiment of control device of the present invention.

The control device 1 of this embodiment comprises a valve case 2provided with a fluid inlet channel 2 a and a fluid outlet channel 2 b,an annular valve seat 3 formed around a peripheral edge defining anopening of the inlet channel 2 a, a diaphragm (valve element) 4 movableinto or out of pressing contact with the valve seat 3 for closing oropening the fluid channel 2 a, a disk (valve element holder) 5 movableupward or downward and having a diaphragm holder 5 a attached to itslower end, a bonnet 6 fitted around the disk 5, a lower casing 7provided on an upper portion of the valve case 2, an upper casing 8joined to the lower casing 7, a valve stem 9 disposed within a spacedefined by the upper and lower casings 7, 8 and having a lower end inbearing contact with the valve element holder 5, a piston 10 disposed inan upper portion of the space defined by the casings 7, 8, and boostermeans 11 disposed in the space defined by the casings 7, 8 below thepiston 10 for transmitting the force acting on the piston 10 to thevalve stem 9 upon amplification.

The valve case 2 has a cavity 2 c which is open upward. The inletchannel 2 a has one end which is open leftward and the other end whichis open at the center of bottom wall of the cavity 2 c. The outletchannel 2 b has one end which is open rightward and the other end whichis open at a right portion of the bottom wall of the cavity 2 c.

The disk 5 is in the form of a solid cylinder and has a flange at anintermediate portion thereof. The bonnet 6 is in the form of a hollowcylinder and has a lower-portion inner periphery providing a guideportion 6 a of large diameter for guiding the flange of the disk 5. Thedisk 5 is fitted in the bonnet 6 loosely, i.e., upwardly or downwardlymovably. The bonnet 6 is fitted in the cavity-2 c of the valve case 2and depressed by the lower casing 7 to thereby cause a holding adaptor12 to secure an outer peripheral portion of the diaphragm 4 to the valvecase 2.

The lower casing 7 comprises a bottom wall 7 a, a peripheral wall 7 bupstanding from the bottom wall 7 a and having an externally threadedportion on its outer periphery, and a hollow cylindrical downwardprojection 7 c of small diameter extending downward from the bottom sideof the bottom wall 7 a and having an internally threaded portion on itsinner periphery. The internally threaded portion of the downwardprojection 7 c is in screw-thread engagement with an externally threadedportion of a peripheral wall of the valve case 2 which wall defines thecavity 2 c, whereby the lower casing 7 is secured to the valve case 2.

A through bore 13 is formed in the bottom wall 7 a of the lower casing 7centrally thereof for guiding the valve stem 9 upwardly or downwardlymovably.

The upper casing 8 comprises a hollow cylindrical peripheral wall 8 aand a top wall 8 b in the form of a disk and screwed in an internallythreaded upper end portion of the peripheral wall 8 a. The peripheralwall 8 a has an internally threaded lower portion, which is screwed onthe externally threaded portion of peripheral wall 7 b of the lowercasing 7, whereby the upper casing 8 and the lower casing 7 are joinedto define the above-mentioned space inside thereof. The top wall 8 b ofthe upper casing 8 has in its center a through bore 14 provided with acompressed air admitting coupling 15.

The valve stem 9 comprises a large-diameter shank 21 having a downwardprojection 21 a slidably inserted through the center through bore 13 ofthe lower casing 7, and a small-diameter shank 22 having an externallythreaded lower-end portion and joined to the large-diameter shank 21with the externally threaded portion screwed in an internally threadedupper portion of the shank 21. The large-diameter shank 21 further has aflange portion 21 b positioned at the base end of the downwardprojection 21 a, and an upper end portion 21 c having a smaller diameterthan the other portion thereof and butted against the small-diametershank 22. The shank 22 has at an intermediate portion thereof a flangeportion 22 a having a slightly smaller diameter than the upper endportion 21 c of the large-diameter shank 21.

The piston 10 is in the form of a disk comprising a large-diameter lowerportion 10 a and a small-diameter upper portion 10 b. An annular pistonring 23 is joined to the outer peripheral portion of lower side of thelarge-diameter portion 10 a. A recessed portion 24 is formed in thelower surface of top wall 8 b of the upper casing 8 centrally thereof. Aspace provided by the recessed portion 24 between the top wall 8 b ofthe upper casing 8 and the piston 10 serves as a compressed airadmitting space.

Provided around the small-diameter portion 10 b of the piston 10 aremetal bellows 16 generally in the form of a hollow cylinder and having alower end secured to the upper surface of the large-diameter portion 10a and an upper end secured to the lower surface of top wall 8 b of theupper casing 8, whereby the compressed air admitting space is sealedoff. The metal bellows 16 are termed welded bellows and are made bystamping out disks from a metal sheet to obtain wavy precision platesand welding the wavy plates along the inner peripheries and outerperipheries thereof

The booster means 11 has a plurality of pivotal members 25 eachsupported by a horizontal rod 26 so as to be pivotally movable about therod. Each pivotal member 25 has its outer end and its inner end broughtinto contact with the lower surface of the piston ring 23 and the lowersurface of the flange portion 22 a of small-diameter shank 22 of thevalve stem 9, respectively, from below. The position where the outer endof the pivotal member 25 is in contact with the piston is at a higherlevel than the position where the inner end of the pivotal member 25 isin contact with the valve stem 9. The axis of the horizontal rod 26 ispositioned closer to the inner end of the pivotal member 26 than themidpoint between the position of contact of the outer end of the member25 with the piston and the position of contact of the inner end of themember 25 with the valve stem 9. Accordingly, when the piston 10 movesdown, the outer end of each pivotal member 25 of the booster means 11moves down, thereby moving the pivotal member 25 about the horizontalrod 26 and moving the inner end of the pivotal member 25 upward to movethe valve stem 9 upward. With the horizontal rod 26 positioned closer tothe pivotal member inner end, the downward force of the piston 10 istransmitted as amplified to the valve stem 9. The ratio of amplificationis (the distance from the axis of the horizontal rod to the position ofcontact of the pivotal member outer end with the piston)/(the distancefrom the axis of the horizontal rod to the position of contact of thepivotal member inner end with the valve stem).

For example, three or four pivotal members 25 are arranged at an angularspacing of 120 degrees or 90 degrees about the axis of the valve stem 9.The horizontal rods 26 are supported by a hollow cylindrical retainer 27positioned on the large-diameter shank 21. The retainer 27 comprises abottom wall 27 a in the form of a disk having a hole, and a peripheralwall 27 b having cutouts formed at predetermined intervals andpermitting the movement of the respective pivotal members 25. The innerend of each pivotal member 25 has an indented portion 25 a facingupward. A pin 28 rollably provided in the indented portion 25 a isadapted to contact the flange portion 22 a of small-diameter shank 22 ofthe valve stem 9.

A biasing member 17 for urging the valve stem 9 downward comprises discsprings and is held by the flange portion 21 b of large-diameter portion21 of the valve stem 9 and the bottom wall 27 a of the retainer 27. Ametal seal 18 is provided around the outer periphery of bottom wall 27 aof the retainer 27 and positioned on the upper end of the peripheralwall of the lower casing 7.

FIG. 1 shows the piston 10 in an upper position, and the valve stem 9biased by the biasing member 17 and located in a lower position, thestem 9 pressing the diaphragm 4 against the annular valve seat 3 toclose the fluid channel. When compressed air is admitted in this statethrough the coupling 15, the piston 10 is moved down, causing thebooster means 11 to move the valve stem 9 upward to move the diaphragm 4away from the annular valve seat 3 and open the fluid channel.

The control device 1 has metal bellows 16 for sealing off the compressedair admitting space, and no O-rings of rubber are used. The devicetherefore has high heat resistance and is capable of withstanding hightemperatures of about 30° C. The booster means 11 incorporated providesa great diaphragm holding force even if the pressure of the compressedair admitted is small, consequently reducing the pressure to be exertedon the metal bellows 16. The control device thus provided andserviceable as a valve for use at high temperatures is thereforeoutstanding also in pressure resistance.

INDUSTRIAL APPLICABILITY

The control device of the invention has booster means for transmittingthe force acting on a piston to a valve stem on amplification, is usableeven at high temperatures and suitable as a valve for use at hightemperatures.

1. A control device comprising a valve case having a fluid channel, acasing provided on an upper portion of the valve case, a valve stemdisposed inside the casing and reciprocatingly movable upward anddownward to cause a valve element to open or close the fluid channel, apiston upwardly or downwardly movably provided inside the casing todefine a compressed air admitting space along with a top wall of thecasing, and booster means for transmitting a force acting on the pistonto the valve stem on amplification, the control device beingcharacterized in that the booster means comprises at least one pivotalmember supported by the casing so as to hold an outer end and an innerend thereof in contact with an outer peripheral portion of the pistonand a flange portion formed on the valve stem respectively from belowand to be pivotally movable about a horizontal rod positioned closer tothe inner end, metal bellows being provided between an outer peripheralportion of the casing top wall and the outer peripheral portion of thepiston for sealing off the compressed air admitting space.